Wind Turbines for the Home (Domestic)

What Is Wind Power?

Wind power relies on the sustainable energy of the wind, which unlike fossil fuels, can't run out. Wind is actually a form of solar energy; winds are caused by the heating of the atmosphere by the sun, the rotation of the earth, and the earth's surface irregularities.

It is a free and readily available source of power on our island nation and is used in large scale wind farms to generate electricity for industry or to supply the National Grid for a greener way to power villages and cities. Smaller scale domestic systems for the home are also becoming more and more common on rooftops and in the grounds of residential properties, schools, farms and small businesses.

How Does it Work?

Converting wind energy to electricity can be explained quite simply - the wind spins the blades of a fan; this in turn drives a turbine creating electricity (just like a dynamo on an old fashioned bicycle).

While the premise is simple the power output can be surprising, if a bit more complicated. Wind power is proportional to the velocity of the wind cubed. If the wind speed doubles, the energy created increases by a factor of 8. To put it in simpler terms, if the wind speed at one location has a value of 10 and in another location the speed is 12. The wind speed in the second location has only increased by 20%, but the available power has increased by 70%.

Most small wind turbines generate direct current (DC) electricity. Systems that are not connected to the national grid require battery storage and an inverter to convert DC electricity to AC (alternating current - mains electricity).

Wind systems can also be connected to the national electricity grid. A special inverter and controller converts DC electricity to AC at a quality and standard acceptable to the grid. No battery storage is required. Any unused or excess electricity may be able to be exported to the grid and sold to the local electricity supply company.

Types Of Wind Turbine Systems

The simplest way to categorise wind turbines available in the UK is Roof mounted or Mast mounted.

Roof Mounted
These are usually smaller units that can be installed on house roofs and other buildings. We would not recommend this type of installation unless your building has been designed to withstand lateral loads. They do have the potential to seem noisy due to the immediate proximity to the building that they are attached to. Turbulence created from the building can also make these systems not reach their true potential. Roof-mounted systems are generally limited in size due to being placed on a building and therefore tend to have lower outputs of 1 Kilo watt (Kw) or below.

Mast Mounted
These are free standing turbines that are situated on top of a mast that can range from 10m to over 30m and are located near the building(s) that will be using the electricity. A mast mounted wind turbine has a number of advantages over a roof-mounted system. There is the greater freedom to site the turbine in the optimum position for the best results. As for any wind turbine a clear line of sight is desired, with a mast this can be easier to obtain than with roof mounting. The speed of the wind increases with height, so the higher the turbine can be situated the better the output. (Instead of having a larger wind turbine, it can sometimes be cost effective to have a smaller system on a taller tower.) Furthermore, the mast can be of a strength that can support larger turbines with outputs that vary between 1 Kw to 6.5 Kw for domestic and up to 15Kw for commercial use. The main issues with a mast-mounted turbine over a roof-mounted system are the higher cost and the extra space needed. While being more expensive, a mast-mounted turbine has the potential for greater return on any investment.

Is It Suitable For My Needs?

Which system is most suitable for your property or project depends on a number of factors that Green Energy Doctor will take into account as part of the design. However, the following are some general principles that will help you decide whether it is a technology you would like to consider in more detail for your property or project:

Wind Speed / Conditions
It is essential that the proposed site of the wind turbine is one that receives sufficient and consistent wind speeds in order to turn the blades. We would recommend a minimum average of 5 metres per sec at 10m above ground level. To find out the general wind speed in your area, please visit our website which will have links to the most up-to-date and appropriate websites of where to find wind speeds for your area.

Positioning & Obstructions
In our experience, only a small percentage of sites are suitable for wind turbines to gain the benefit required to make them economical. It is critical in siting a wind turbine that it is well clear of large obstacles, especially in the path of the prevailing wind. There has to be a good line of sight from the turbine. If the turbine is too near to large obstacles such as buildings, trees or hills the true potential of the system will be difficult to attain. As a general rule:

• If the turbine has to be placed behind an obstruction, it should be ten times the height of said obstruction.
• If the mast is to be placed in front of a building, to avoid any turbulence, it should be twice the height.
• They are of limited effectiveness in built up urban areas.

Energy Requirements
One disadvantage is that wind power is an intermittent power source. The production from a wind turbine may increase or decrease dramatically over a short period of time with little or no warning. Therefore, turbines are used, generally, to supplement other sources of power as from solar panels or the National Grid.

Aesthetics
Aesthetics should be a major consideration when installing a wind turbine. Turbines have often to be located on high and very visible places, with possible negative aesthetic impacts. Your wind turbine would be a clear sign to your neighbours or customers that you are making the effort to reduce your carbon footprint, however it can be a good idea to discuss your plans with them, as they will have to live with it also, without reaping any of the benefits.

Planning Permission
Most rooftop turbines will require planning permission because of the necessity to site the apparatus above the ridge height of the building. Green Energy Doctor can help to advise you on whether planning permission would be needed.

What Are The Benefits?

Reduce Your Energy Bills
Wind energy is one of the lowest-priced renewable energy technologies available today. With the correct location and a turbine system that is sized correctly according to your power requirements, you can expect to save between 25 - 30% off your electricity annually.

Reduce Your Impact On The Environment
Wind energy is fuelled by the wind, so it's a clean fuel source. Wind energy doesn't pollute the air like power plants that rely on combustion of fossil fuels, such as coal or natural gas. Wind turbines don't produce atmospheric emissions that cause acid rain or greenhouse gasses.

Reduce Your Dependency On Fossil Fuel Imports
The wind is a free source of energy and is estimated to be secure for the next few million years. This can provide you with the peace of mind that a significant proportion of your energy is under your control and will not increase in price as a result of foreign government actions or the prevailing economic climate.

Sell Surplus Electricity Back To Grid
If your wind turbine is producing more electricity than you require, the excess can be exported back onto the National Grid using an export meter. The rate paid various from company to company but some tariffs offer over 10p per kWh.

Sell Renewable Obligation Certificates (ROC’s)
Eligible sustainable generators, including consumers are awarded these digital certificates for every 1000kwhrs of electricity generated. Energy Companies are required to generate a minimum level of their electricity output from sustainable sources. If they have not managed to produce the required amount of green energy themselves they must buy ROCs on the open market to make up the shortfall. This certificate can be sold to electricity suppliers for up to £40, this equates to an additional 4p per kWh.

Typical Outputs and Costs

Wind Turbines are rated at peak output power in standard test conditions. These conditions are rarely achieved consistently in practice as the output fluctuates with a number of variables such as wind speeds, and turbulence, which vary considerably during the day and also during the year. However, below will give you an indication of the typical outputs by system size that is located in a suitable location and installed professionally:

Turbine Size	1KW	1.5Kw	2.5Kw	6Kw	15Kw
Applications	Domestic properties	Domestic properties	Domestic & small business premises lighting	Domestic, schools, smallholdings and small commercial units	Small industrial unit application
Rated Output	1000W	1500W	2500W	6000W	15000W
Annual Output (kWh)	1000-2000	1500-3000	2,500-5,000	6,000-12,000	15,000-30,000
Typical Rotor Diameter:	<1.5m	<2m	3.5m	5.5m	9m
Estimated Costs (including Installation)	£2,000	£6,000	£11,000 - £15,000	£19,000 - £24000	£40000-£46,000
Estimated Payback	Limited data	Limited data	7-10 years	5-8 years	3-7 years

• Please remember there are many variables and types of system that can affect outputs, pricing and payback. These are a guideline only for affordability.
• Excluding Grants

How to Get Started...

To organise a no obligation site visit or to start moving your project forward contact the Green Energy Doctor today on:

T: 0845 009 5652
E: info@greenenergydoctor.co.uk